Apparatus for microfinishing crankpins of crankshafts



De.22;;1970 H,RUNGE ETAL 3,548,547

APPARATUS FOR MICROFINISHING CRANKPINS OF CRANKSHAFTS Filed June 21,196'? 5 Sheets-Sheet 1 s 0 25 4 21 a O Q a e /N VE N TORS ATTYJ.

- Dec. 22, 1970 1 RUNGE ETAL 3,548,547

APPARATUS FOR MICROFINISHING CRANKPINS CRANKSHAFTS Filed June 21, 1967 vSheets-Sheet 2 INVENTORS: H. Ru/vaE 4- K. W/EC ATTY Dec. 22,19703,548,541

APPARATUS FOR MICROFINISHING CRANKPINS OF CRANKSHAFTS Filed June 21,1967 HVRUNGE ETAL 5 Sheets-Sheet 3 Ian- INVENTORS: H. Ru/vaE 947K WIECKATTY DEC. 22, 1970 RUNGE ET AL 3,548,547

APPARATUS FOR MICROFINISHING CRANKPINS OF GRANKSHAFTS Filed June 21,1967 Sheets-Sheet 4 Fig.6 55 55 49 "14/9, o I 66 g 0 o o O 54 57 2 56 3a EX 3 60 IN VE N TOPS H Ru/vcE 9" K. M'Ecn Q LMM Dec. 22,1970 H. @NG:ETAL 3,548,541

APPARATUS FOR MI CROFINISHING CRANKPINS OF CRANKSHAFTS Filed June 21,1967 5 Sheets-Sheet 5 IN VE N TOPS H. Kali/05.5 K. W/ECK Z gfiww UnitedStates Patent, M

ABSTRACT OF THE DISCLOSURE A device for highly accurate microfinishingof the crankpins of crankshafts as the crankshaft is supported on alathe which rotates the crankshaft about its axis of rotation Theaccurate microgrinding or microfinishing of crankpins has been asubstantial problem in the art because the crankpins follow a circularpath of movement about the crankashaft as the crankshaft is rotatedabout its axis. In the present apparatus, the microgrinding ormicrofinishing head, or appliance carrier, is mounted on a supportingarm means which is so constructed that the transverse working axis ofthe microfinishing head remains closely parallel to the axis of thecrankshaft and its supporting lathe, while at the same time themicrofinishing head freely follows the circular path of the crankpin.This accurate control of the microfinishing head insures that thecrankpin will be ground to a desired precision not possible with priorknown apparatus or methods for performing the same operation. The basicconcept takes several alternate forms.

BACKGROUND OF THE INVENTION In order to achieve high precision in themanufacturing or repair of crankshafts, so that the crankshafts willrotate smoothly in their bearings without vibration, it has becomedesirable to microfinish the crankshafts in general, and particularlythe bearing pins of the crankshafts. The smooth action of the pistonrods and the durability of the engine are closely related to the qualityof such microfinishing. The microfinishing of the bearing pins ofcrankshafts has not been particularly difficult, since the bearing pinsduring rotation of the crankshaft on the lathe rotate about a fixedaxis, remaining in substantially the same position. Therefore, themicrofinishing device for finishing the said bearing pins may be fixedlymounted and so held until the desired microfinishing is completed.However, microfinishing of the crankpins of the crankshafts has beensubstantially more difiicult, because the crankpin moves in a circularpath around the bearing pins on the axis of rotation of the crankshaft.Grinding of the crankpins before assembly is not feasible, because thegrinding must be done in situ on a completed crankshaft. Further, themicrofinishing is often undertaken on crankshafts being repaired.

Prior grinding devices have been known in which the microfinishing head,sometimes called the appliance carrier, is guided by and held on thecrankpin itself. In this apparatus, the microfinishing head mustcompletely surround the crankpin. It is aligned on the crankpin in sucha way that the microfinishing head, as a multiple part frame, engages onthe transition rods between the crankpin and the cheeks of thecrankshaft by means of adjust ing screws or spring-loaded bolts. In thisstructure, rota tion of the frame around the axis of the pin ispossible. Grinding is effected in that either the microfinishing headframe rotates around the crankpin of the crankshaft while Patented Dec.22, 1970 l-CG it is at rest, or the frame is held while the crankshaftis rotated about its axis of rotation. In neither case does themicrofinishing head have any rigid support or fixed position relative toa stationary base. The centering of the frame on the crankpin is notaccurate because the necessary spring adjustment of the frame permitsundesirable movement. Irregularities on the transition rods of the pinin this case may be transferred to the microfinishing head, and thus tothe microfinishing tools. In this known apparatus, only relativelycoarse aftergrinding may be undertaken and real microgrinding orsuperfinishing with any accuracy or precision is not possible.

SUMMARY 'OF THE INVENTION It is an object of the invention to make adevice for microfinishing crankpins of crankshafts, in which despite thecircular path of movement of the crankpin around the axis of rotation ofthe crankshaft, the microfinishing head may be easily adjusted and thenmaintained in accurate position during use. This device formicrofinishing crankpins of crankshafts, in which there is relativerotation between the microfinishing tools and the crankpin ischaracterized in that the appliance carrier or microfinishing head iscarried by a mounting which is so formed as to maintain the transverseworking axis of the microfinishing head accurately parallel to the axisof rotation of the crankshaft while the said microfinishing head followsthe circular path of movement of the crankpin about the crankshaft.

In the construction of the present invention, the setting up andalignment of the microfinishing device is independent of the form andnature of the transition rods of the crankshaft relative to the checksof the crankshaft. The microfinishing head is supported on a stable andaccurate mount which permits the microfinishing head to follow thecrankpin without affecting the fineness and accuracy of the workingprocess. Guidance of the microfinishing device is considerably moreexact than if the microfinishig head is carried by and supporteddirectly on the crankpin. The working accuracy of the microfinishinghead is considerably increased, and there is less apparatus Wear.

The construction of the mounting means having the noted capability maybe carried out in various ways. In the preferred embodiment, there is aparallel arm guide means made up of two sets of parallel arms or rails,the microfinishing head being supported at the free end of a pair ofparallel rails. This parallel linkage arrangement makes possible auniform relative speed between the microfinishing tools and the crankpinso that no additional shaping error is introduced into the grindingprocess and a correction of any eccentricity or irregularity of thecrankpin is achieved. The device may be used equally well on newcrankashafts or upon those under repair.

It is an object of the invention to provide other embodiments involvingthe general concept and which may be used for the purpose described.

DESCRIPTION OF THE DRAWINGS FIGURE 1 shows a side elevational view,partly schematic, of a preferred embodiment of the present inven tion.

FIG. 2 is a top plan view, partly diagrammatic, of the transport slidefor the microfinishing head.

FIG. 3 is an end view, partly diagrammatic, of a microfinishing head.

FIG. 4 is a cross-sectional view taken on the line IV-IV of FIG. 2.

FIG. 5 is a longitudinal sectional view taken on the line V-V of FIG. 3.

FIG. 6 is a side elevational view, partly diagrammatic, of a secondembodiment of the invention.

FIG. 7 is a side elevational view, partly diagrammatic, showing stillanother embodiment of the invention.

FIG. 7a is a top fragmentary view of a portion of the structure shown inFIG. 7.

FIG. 8 discloses a final modification of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment for themicrofinishing of crankshafts is shown in FIGS. 1 to 5. A crankshaft 3having crankpin 2 is shown diagrammatically, this crankshaft beingmounted in a well-known manner, not shown, in a lathe or like rotatingdevice which turns the crankshaft about a fixed axis of rotation. Theapparatus 4 of the present invention is adapted to follow continuously acircular movement of the crankpin 2 about the axial center of bearingpin 3 of the crankshaft. On a stationary frame F, the details of whichdo not form a part of the invention, is mounted a support 5 whichcarries a parallel guide linkage. This linkage comprises two sets ofparallel rails 6 and 7, respectively. The parallel rails 6 are pivotedat 8 and 9 on the frame 5 and at 10 and 11 on an intermediate plate 12,while parallel rails 7 are pivoted at 13 ant 14 on the intermediateplate 12 and at 15 and 16 on a holding plate 17. A microfinishing heador appliance carrier 18 is mounted on the holding plate 17. Thus, themicrofinishing head is guided by the parallel guide linkage in acircular path with crankpin 2 about bearing pin 3 in such a way that thetransverse working axis of the microfinishing head and the axis ofrotation of the crankshaft always remain parallel one to the other. Thepivotal joints of rails 6 and 7 are preferably guided by ball bearings.

The microfinishing head 18 serves to support and house thesuperfinishing devices 19 and 20 with their transport slides 21 and 22.The superfinishing head consists of end plates 23 and 24, which areconnected together by elon gated spacing rods 25. The support andguidance of the microfinishing head 18 on the crankpin 2 to be ground isprovided by rollers 26 and 27 journaled in suitable bearings. Theserollers are supported only at their ends, and engage the curved surfaceof the crankpin 2.

Transport slides 21 and 22 support the superfinishing devices 19 and 20and give these devices a gradual advance along or transverse of thelength of the crankpin 2. The advance of the transport slides isprovided by a stepping mechanism 28 (FIGS. 4 and 5) incorporated in eachtransport slide 21 or 22. This stepping mechanism is preferablypneumatically operated.

Each transport slide is guided on two hardened guide rods 29 and 30, andis provided with suitable bearings 31 and 32. The stepping mechanism 28moves the transport rods 29 and 30, and is provided with suitablebarings 31 slide by means of a nut 33, set in each slide, which isthreadedly engaged with a threaded spindle 34, attached between the sideplates 23 and 24 of the superfinishing head. A cam or toothed wheel 35is keyed to the nut 33, so that rotation of the toothed wheel will causerotation of the nut. Each transport slide has pitsons 38 and 39 movablein cylinders 36 and 37, respectively. These cylinders are preferablyoperated pneumatically. The pistons are attached to piston rods 40 and41 respectively and these carry ratchets 43 and 44 respectively. Eachratchet is biased inwardly by a spring 42. These ratchets 43 and 44 haveouter projections which engage the spaces between the teeth 35a of thetoothed wheel 35. The piston cylinder unit 36-38 serves to move toothedwheel 35 and the nut 33 in one direction of rotation, while the pistoncylinder unit 37-39 serves to move wheel 35 in the opposite direction.When the ratchet 43 is engaged, the ratchet 44 is retracted, as shown inFIG. 4. Reversal of the direction of the transport slide takes place atthe end position of the transport slide by selective pneumaticactivation of one or the other of the two cylinders. Nut 33 is providedwith ball bearings 47. The number of steps 4 permitted in the steppingdevice is related to the revolutions per minute of the lathe. The numberof switching steps is dependent upon the diameter of the crankpin to beground.

The superfinishing devices 19 and 20, which are well known and thedetails of which are not a part of the present invention, hang on thetransport slides 21 and 22, respectively. The tools on thesuperfinishing devices 19 and 20 may be advanced toward or withdrawnfrom the work pneumatically by manually operated control rods, notshown. The surface pressure of the tools on the work may be regulated bya pressure-relief valve, these details not being part of the inventionherein described and claimed.

As the crankpin 2 describes a circular path about the axis 3 of thecrankshaft, the superfinishing head is supported by rollers 26 and 27 onthe whirling and rotating crankpin 2. The parallel linkage maintains theaxis of the superfinishing head parallel to the axis of the crankshaft3. The holding plate 17 accurately positions the microfinishing head asthe transport slides 21 and 22 move the tools along the work.

In the embodiment in FIG. 6, the parallel linkage is replaced by a guidearm rod 50 which supports the microfinishing head 48 and themicrogrinding device 49. The arm 50 is made up of sections 51 and 52which are pivotally joined together at 53. The microfinishing head 48 isattached to the free end of the forward section 51. The microfinishinghead is guided and supported on the crankpin 2 by means of the fork 54and projecting arm 55, which carry rollers 56 and 57, respectively. Theguide arm section 52 is pivotally attached at 59 to the frame 60, which,in turn, is carried by the cross-slide 61, the latter forming no part ofthe invention. The crankpin is sup ported at its bearing pins 3 in theblock 62 which has adjustable supporting parts 63. The guide arm 50,when the microfinishing device is not in actual use on a crankpin 2, may'be supported by a fluid operated ram 64. Similarly, the guide armsection 51 is held in stopped position by means of a bolt 0r pin 65.When the device is used, the bolt connection 66 for the ram 64 and thebolt or pin 65 should be released. A conduit 67 shown only infragmentary manner serves for conducting a power supply to themicrofinishing head.

FIG. 7 shows a further embodiment of the device in which the support forthe microfinishing head 69 consists of a rod 68. A microgrinding device70 is carried by the microfinishing head, and likewise a guide part 71provided with rollers 72. The inner end of rod 68 is pivotally attachedas at 73 on slide elements 74 which move along the slide tracks 75 of asupport 76. The slide tracks 75 are perpendicular to the axis ofrotation of the crankshaft 3. Rod 68 may, if desired, be formed oftelescopic sections. The slides 74, as shown in FIG. 7a, are spacedapart but are connected together by the pin or bolt 73, so that the rod68 may swing freely between the said; slide elements.

In the embodiment of FIG. 8, a telescopic rod 77 is provided which ispivoted at 77a to a stationary base B. On the outer end of thetelescopic rod 77, a microfinishing head 78 is pivotally supported as at79. The microfinishing head 78 consists of at least two separable partswhich when joined embrace the crankpin 2. The grinding stones 80 areradially directed and biased toward the crankpin 2 by the springs 81.

What is claimed is:

1. Apparatus for microfinishing a crankpin of a crankshaft as saidcrankshaft is rotated about its axis and said crankpin moves in acircular path about said crankshaft, comprising microfinishing toolmeans for engagement with the surface of said crankpin and means tosupport said microfinishing too], said support means comprising astationary frame member adjacent said crankshaft, at least two sets ofparallel links, an intermediate connecting means, and a tool head, oneend of the first set of parallel links being pivotally connected to saidframe, one end of the second set of parallel links being pivotallyconnected to said tool head means, said microfinishing tool means beingsecured to said tool head means, and the opposite ends of both saidfirst and second sets of parallel links being pivotally connected to anintermediate con necting means, whereby said microfinishing tool meansis free to move with respect to said crankpin as it rotates about saidcrankshaft to provide a substantially uniform speed between saidcrankpin surface and said microfinishing tool means.

2. Apparatus for microfinishing a crankpin of a crankshaft as saidcrankshaft is rotated about its axis and said crankpin moves in acircular path about said crankshaft, comprising microfinishing toolmeans for engagement with the surface of said crankpin and means tosupport said microfinishing tool, said support means including means tomove said tool head means with respect to said crankpin as it rotatesabout said crankshaft to provide a substantially uniform feed betweensaid crankpin surface and said microfinishing tool means and means toprovide reciprocal movement to said microfinishing tool means in a pathparallel to said crankshaft axis along said crankpin surface, saidreciprocal movement providing means including a pair of spaced endplates, parallel guide rods connecting said plates, a transport slideguided by said rods and carrying said microfinishing tool means thereon,and means for controlling movement of said transport slide along saidrods.

3. An apparatus as defined in claim 1 wherein said tool head meansinclude roller members mounted thereon to engage said crankpin surface.

4. An apparatus as defined in claim 3 wherein said tool head meansincludes a U-shaped frame providing leg working members which straddlesaid crankpin,

said roller members being located adjacent the bight of said U-shapedframe.

5. An apparatus as degned in claim 1 wherein said means for controllingmovement of said transport slide comprises a step-by-step actuatormeans.

6. An apparatus as defined in claim 5 wherein said actuator meansincludes a threaded rod extending between said end plates, nut means onsaid transport slide in threaded engagement with said rod, and ratchetmeans for step-by-step rotation of said nut means. 7. An apparatus asdefined in claim 5 wherein said actuator means includes means to reversesaid transport slide when it reaches each end of a desired path ofmovement.

8. An apparatus as defined in claim 1 wherein said means for controllingmovement of said slide comprises a threaded rod extending between saidend plates, a nut means on said transport slide in threaded engagementwith said rods, ratchet means for step-by-step rotation of said nut ineither direction of rotation and control means for actuating the ratchetmeans in the selected direction of rotation.

References Cited UNITED STATES PATENTS LESTER M. SWINGLE, PrimaryExaminer

